“...the whole of the matter of the solar system once formed a globular or spheroidal mass of intensely heated gases, extending beyond the orbit of the outermost planet, and having a slow motion of revolution about an axis. As it cooled and contracted, its rate of revolution increased, and this became so great that at successive epochs it threw off rings, which, owing to slight irregularities, broke up, and, gravitating together, formed the planets. The contraction continuing, the sun, as we now see it, was the result.” (A. R. Wallace, 1904, p. 112.)

• generic condensation produces dust and smaller bodies
• formation of protoplanetary disc
• "Colder" planetesimals accumulate due to gravity
• Accretion theories: updated planetesimal view

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